1. Field of the Invention
The present invention relates to processes for enzymatic refining of a pretreated cellulosic material using one or more esterase enzymes. The refined pretreated cellulosic material is suitable for saccharification.
2. Description of the Related Art
Cellulose is a polymer of the simple sugar glucose covalently linked by beta-1,4-bonds. Many microorganisms produce enzymes that hydrolyze beta-linked glucans. These enzymes include endoglucanases, cellobiohydrolases, and beta-glucosidases. Endoglucanases digest the cellulose polymer at random locations, opening it to attack by cellobiohydrolases. Cellobiohydrolases sequentially release molecules of cellobiose from the ends of the cellulose polymer. Cellobiose is a water-soluble beta-1,4-linked dimer of glucose. Beta-glucosidases hydrolyze cellobiose to glucose.
The conversion of lignocellulosic feedstocks into ethanol has the advantages of the ready availability of large amounts of feedstock, the desirability of avoiding burning or land filling the materials, and the cleanliness of the ethanol fuel. Wood, agricultural residues, herbaceous crops, and municipal solid wastes have been considered as feedstocks for ethanol production. These materials primarily consist of cellulose, hemicellulose, and lignin. Once the lignocellulose is converted to fermentable sugars, e.g., glucose, the fermentable sugars are easily fermented by yeast into ethanol. The sugars can also be catalytically converted or fermented to other chemicals besides ethanol.
The conversion of lignocellulosic feedstocks into sugars, typically, involves pretreatment of the cellulosic materials, followed by their enzymatic hydrolysis, prior to the conversion of the sugars into fermentation products or catalytically converted products. The pretreatments disrupt the lignocellulosic material, so enzymatic hydrolysis can take place efficiently.
However, pretreatment of cellulosic materials can produce impurities in the pretreated cellulosic materials having a deleterious effect on cellulase enzymes and/or decreases or inhibits enzymatic hydrolysis and/or saccharification.
It would be advantageous to the art to be able to improve the pretreated cellulosic material for saccharification. For example, it would be advantageous in the art to improve the enzymatic hydrolysis performance of pretreated cellulosic material such as biomass including corn stover, wood chips, switch grass, etc by reducing, eliminating or removing impurities such as esters that have a deleterious effect on the cellulase enzymes.
Prior art of interest includes WO 2009/042622 A2 which discloses a process for producing fermentation product from wood-containing material, wherein the process includes the steps of i) pre-treating wood-containing material; ii) hydrolyzing by subjecting the pre-treated wood-containing material to one or more cellulolytic enzymes; iii) fermenting using a fermenting organism, wherein the wood-containing material is subjected to one or more esterases before and/or during pre-treatment in step i) and/or hydrolysis in step ii) and/or fermentation in step iii).
The present invention relates to processes for enzymatically assisted refining of a pretreated cellulosic material for saccharification.